The present invention relates to an ink jet recording head suitably used for recording apparatuses such as printers and plotters, and more particularly, to an ink jet recording head in which a fixation base of a vibrator unit is bonded to a case.
Some related ink jet recording heads (hereinafter, referred to as recording heads for short) have a structure provided with: a vibrator unit in which a piezoelectric vibrator row is joined to a fixation base; a case in which a housing space capable of housing the vibrator unit is formed, and a channel unit joined to a distal end of the case.
The vibrator unit is a member formed by joining piezoelectric vibrators and the fixation base into a single unit. In this vibrator unit, the fixed ends of the piezoelectric vibrators are joined to the fixation base, for example, in a so-called cantilevered manner in which the free ends of the piezoelectric vibrators protrude outside a distal end face of the fixation base. The case is a block-shaped member molded of a synthetic resin and is provided with a flat housing space whose top and bottom are open and that has a size in which the vibrator unit is exactly fitted. The channel unit is a plate-shaped member having an interior of an ink channel communicating a common ink reservoir and a nozzle orifice via a pressure chamber.
To assemble this recording head, the channel unit is bonded to a distal end face of the case, and the vibrator unit is housed and fixed in the housing space of the case. The vibrator unit is fixed by bonding together the fixation base and a bonding wall formed inside the case. For example, a fluid adhesive is poured into a gap between bonding faces of the fixation base and the bonding wall, and the poured adhesive is cured.
In the recording head of this structure, it is of vital importance that the bonding area of the fixation base and the bonding wall, particularly, the area corresponding to the fixed ends of the piezoelectric vibrators contain no residual bubbles and are filled with the adhesive. This is because, if the adhesive is insufficiently filled in the bonding area and bubbles remain, the part corresponding to the residual bubbles is low in rigidity and this affects the behavior of the piezoelectric vibrators so that ink drop jetting characteristics such as the flying speed and the ink amount changes.
The present invention is made in view of these circumstances, and an object thereof is to provide an ink jet recording head in which bubbles remaining in the bonding area of the fixation base and the bonding wall are prevented.
In order to achieve the above object, according to the present invention, there is provided an ink jet recording head, comprising:
a vibrator unit, in which a plurality of piezoelectric vibrators are arranged on a base member in a cantilevered manner;
a case, formed with a housing space having a bonding area at which a first inner portion of the housing space and a first face of the base member are opposed with a gap;
at least one adhesive inlet, from which an adhesive is poured, the adhesive inlet communicating with the bonding area; and
at least one air outlet, from which air remaining in the bonding area is expelled as the poured adhesive fills the gap.
In this configuration, the gap in the bonding area is gradually filled by the influent adhesive from the side of the adhesive inlet while air in the bonding area is expelled toward the air outlet side, so that it can be prevented that air bubbles remain in the bonding area. Consequently, partial lack of rigidity in the bonding area can be prevented, so that the behavior of the piezoelectric vibrators can be made the same. As a result, ink drop jetting characteristics such as the flying speed and the ink amount can be stabilized.
Preferably, a pair of adhesive inlets are disposed so as to face both lateral side edge portions of the bonding area, and the air outlet is disposed between the adhesive inlets.
Alternatively, it is preferable that a pair of air outlets are disposed so as to face both lateral side edge portions of the bonding area, and the adhesive inlet is disposed between the air outlets.
Alternatively, it is preferable that the adhesive inlet is disposed so as to face one lateral side edge portion of the bonding area, and the air outlet is disposed so as to face the other lateral side edge portion of the bonding area.
Preferably, a dimension of the gap is so determined as to establish capillarity from the adhesive inlet to the air outlet.
In this configuration, the poured adhesive fills the gap in the bonding area from the side of the adhesive inlet toward the air outlet by a capillary force. Since the strength of the capillary force can be controlled, the adhesive filling speed in the bonding area can positively be controlled. Consequently, the air in the bonding area can reliably be expelled.
Here, it is preferable that the dimension of the gap is reduced as being away from the adhesive inlet and being close to the air outlet.
In this configuration, the capillary force of the adhesive increases with distance from the adhesive inlet. Consequently, the adhesive poured in the adhesive inlet can reliably be directed to the air outlet.
Preferably, a pair of rib members extending in a vertical direction is formed in the housing space, and disposed both lateral sides of the bonding area. Each of the rib members has a face which is in close contact with the first face of the base member. The adhesive inlet is disposed between the rib members.
In this configuration, since the poured adhesive is dammed by the rib members which are in close contact with the base member, the adhesive can be held in the bonding area. Consequently, the problem wherein the adhesive adheres to other parts can reliably be prevented.
Preferably, the recording head further comprises an adhesive reservoir provided between the adhesive inlet and the bonding area in order to store the poured adhesive temporarily.
In this configuration, it can be made difficult for the adhesive to flow out from the adhesive inlet even if the adhesive pouring speed is increased. This reduces the time necessary for the bonding step.
Here, it is preferable that a capacity of the adhesive reservoir is so determined as to store an amount of adhesive which is enough to fill the gap in the bonding area.
In this configuration, pouring of the adhesive can be finished only once. Consequently, the time necessary for the bonding step can be further reduced.
Preferably, a dimension of the gap at a portion where the bonding area communicates with the air outlet is determined such that the adhesive is held thereat due to surface tension thereof.
In this configuration, the adhesive in the bonding area can be prevented from flowing into the air outlet.
Preferably a second inner portion of the housing space which situates an upper portion of the first inner portion is retracted so as to be away from the base member fixed on the first inner portion, to form a non-bonding area. A top portion of the first inner portion is tapered so as to continue to the non-bonding area so that the gap thereat is enlarged toward the non-bonding area, thereby filling condition of the poured adhesive in the tapered portion can be externally confirmed.
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In this configuration, whether the adhesive is filled in the entire bonding area or not can be determined based on the filling state of the adhesive in the tapered portion. Consequently, poor bonding can be prevented.
Preferably, a third inner portion of the housing space which faces the piezoelectric vibrators is protruded from the first inner portion so as to form a step portion on which a second face of the base member is bonded. A corner portion of the step portion which is closer to the piezoelectric vibrators is recessed so as to be away from the piezoelectric vibrators.
Here, it is preferable that a part of the second face of the base member which faces the recessed corner portion of the step portion is recessed so as to be away from the corner portion.
In this configuration, the adhesive can be held in the step portion while the adhesive is prevented from reaching the piezoelectric vibrators.